Exemplary embodiments relate to nanodevices, and more specifically, to piezoelectric-based nanopores.
Recently, there has been growing interest in applying nanopores as sensors for rapid analysis of biomolecules (DNA, RNA, protein, etc). Special emphasis has been given to applications of nanopores for DNA sequencing, as this technology holds the promise to reduce the cost of sequencing below $1000/human genome. An issue in these applications is the control of the translocation of DNA through the nanopore.
Nanopore sequencing is a method for determining the order in which nucleotides occur on a strand of DNA. A nanopore is simply a small hole of the order of 1 nanometer in internal diameter. The theory behind nanopore sequencing has to do with what occurs when the nanopore is immersed in a conducting fluid and a potential (voltage) is applied across it: under these conditions a slight electric current due to conduction of ions through the nanopore can be observed, and the amount of current is very sensitive to the size and shape of the nanopore. If single bases or strands of DNA pass (or part of the DNA molecule passes) through the nanopore, this can create a change in the magnitude of the current through the nanopore. Other electrical or optical sensors can also be put around the nanopore so that DNA bases can be differentiated while the DNA passes through the nanopore.
DNA could be passed through the nanopore for various reasons. For example, electrophoresis might attract the DNA towards the nanopore, and it might eventually pass through it. Also, enzymes attached to the nanopore might guide DNA towards the nanopore. The scale of the nanopore means that the DNA may be forced through the hole as a long string, one base at a time, rather like thread through the eye of a needle. As it does so, each nucleotide on the DNA molecule may obstruct the nanopore to a different, characteristic degree. The amount of current which can pass through the nanopore at any given moment therefore varies depending on whether the nanopore is blocked by an A, a C, a G or a T. The change in the current through the nanopore as the DNA molecule passes through the nanopore represents a direct reading of the DNA sequence. Alternatively, other electrical or optical sensors can also be put around the nanopore to identify individual DNA bases as they pass through the nanopore in the correct order. The potential of this nanopore DNA sequencing approach is that a single molecule of DNA can be sequenced directly using a nanopore, without the need for an intervening PCR amplification step or a chemical labeling step or the need for optical instrumentation to identify the chemical label.